The organ preservation effect of opioids is examined in a single organ preservation preparation. Rat lungs are dissected and preserved in hypothermic solutions with or without a delta opioid peptide DADLE. DADLE markedly enhances the hypothermic preservation time of isolated rat lungs. The functions of the hypothermically preserved lungs with added DADLE are comparable to the functions of the controls which are dissected and studied immediately. Lungs preserved without DADLE functioned poorly in the test.